A boy and a girl are sitting on the porch.
"I'm a boy," says the child with black hair.
"I'm a girl," says the child with red hair.
If at least one of them is lying, who is which?

You have two rectangular wires.

Both of them have property that when you light the fire from one end , it will take 60 minutes to get completely burn.

However, they do not burn at consistent speed (i.e it might be possible 1st 20% burn in 50 minutes and 80% can burn in 10 minutes).

So how could you measure 45 minutes ?

Can you count the number of matches in the picture below ?

A plane crashed between the border of Mexico and America. Where do you bury the survivors?

Count the number of lines in the image below ?

What occurs twice in a week, once in a year but never in a day?

why number 8549176320 is one of a kind?

John was working on a Chemical Mixture whose weight comprise 90% liquid and 10% solid. The total weight of the mixture is 20 pounds. After a while, John noticed that some of the liquid evaporated and now the liquid comprises just 50% of the weight.

What is the weight of the chemical mixture now?

The person who makes it has no need for it. He who purchases it does not use it. The person who does use it does not know they are. What is it?

If 21x = 79x, what is the value of x?